Parse command-line arguments

Parse command-line arguments is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Command-line arguments can be quite complicated, as in "nc -v -n -z -w 1 192.168.1.2 1-1000". Many languages provide a library (getopt or GetOpt) to parse the raw command line options in an intelligent way.

Icon and Unicon

The Icon Programming Library provides a procedure for processing command line options. See the library reference for detailed documentation. The code below is an example.

<lang Icon>link options

procedure main(ARGLIST) /errproc := stop # special error procedure or stop() opstring := "f!s:i+r.flag!string:integer+real." # example opttable := options(ARGLIST,optstring,errproc)

if \opttable[flag] then ... # test a flag r  := opttable(real) # assign a real r2 := opttable(r) # assign another real s  := opttable(s) # assign a string i  := opttable(i) # assign an integer ... end</lang>

Library: Icon Programming Library

options.icn supports getting command-line options

J

When J starts up from the command line, the command line arguments are available in the array ARGV. On modern machines, the first command line argument is the name of the executable (the J interpeter, in this case).

Typically, the next argument (if present) is the name of a file whose contents will be executed.

Further command line analysis might include:

Test if an argument is present:

<lang j> (<'-b') e. ARGV</lang>

This is true if the argument is present and false, if it is not.

Or, find the name of an optional file:

<lang j> (ARGV i.<'-f') {:: ARGV,a:</lang>

This is the name of the first file named after the first -f argument, or blank if there was no such file.

Other concepts are also possible...

PicoLisp

PicoLisp doesn't have a library to get options. Instead, the command line is parsed at startup and handled in the following way: Each command line argument is executed (interpreted) as a Lisp source file, except that if the first character is a hypen '-', then that arguments is taken as a Lisp function call (without the surrounding parentheses). For example, the command line <lang shell>$ ./pil abc.l -foo def.l -"bar 3 4" -'mumble "hello"' -bye</lang> has the effect that

1. The file "abc.l" is executed
2. (foo) is called
3. The file "def.l" is executed
4. (bar 3 4) is called
5. (mumble "hello") is called
6. (bye) is called, resulting in program termination

Command line arguments like "-v", "-n" and "-z" can be implemented simply by defining three functions 'v', 'n' and 'z'.

In addition to the above mechanism, the command line can also be handled "manually", by either processing the list of arguments returned by 'argv', or by fetching arguments individually with 'opt'.

Ruby

Ruby's standard library provides two different packages to parse command-line arguments.

• 'getoptlong' resembles the libraries from other languages.
• 'optparse' has more features.

Ruby with 'getoptlong'

<lang ruby>#!/usr/bin/env ruby

1. == Synopsis
3. pargs: Phone a friend
5. == Usage
7. pargs [OPTIONS]
9. --help, -h:
10. show usage
12. --eddy, -e <message>
13. call eddy
15. --danial, -d <message>
16. call daniel
18. --test, -t
19. run unit tests

require "getoptlong" require "rdoc/usage"

def phone(name, message) puts "Calling #{name}..." puts message end

def test phone("Barry", "Hi!") phone("Cindy", "Hello!") end

def main mode = :usage

name = "" message = ""

opts=GetoptLong.new( ["--help", "-h", GetoptLong::NO_ARGUMENT], ["--eddy", "-e", GetoptLong::REQUIRED_ARGUMENT], ["--daniel", "-d", GetoptLong::REQUIRED_ARGUMENT], ["--test", "-t", GetoptLong::NO_ARGUMENT] )

opts.each { |option, value| case option when "--help" RDoc::usage("Usage") when "--eddy" mode = :call name = "eddy" message = value when "--daniel" mode = :call name = "daniel" message = value when "--test" mode = :test end }

case mode when :usage RDoc::usage("Usage") when :call phone(name, message) when :test test end end

if __FILE__==$0 begin main rescue Interrupt => e nil end end</lang>

$ ./pargs.rb -h

Usage
-----
pargs [OPTIONS]

--help, -h:

   show usage

--eddy, -e <message>

   call eddy

--daniel, -d <message>

   call daniel

--test, -t

   run unit tests

$ ./pargs.rb -e Yo!
Calling eddy...
Yo!
$ ./pargs.rb --test
Calling Barry...
Hi!
Calling Cindy...
Hello!

Ruby with 'optparse'

<lang ruby>require 'optparse'

sflag = false longflag = false count = 0 percent = 50 fruit = nil

OptionParser.new do |opts|

 # Default banner is "Usage: #{opts.program_name} [options]".
 opts.banner += " [arguments...]"
 opts.separator "This demo prints the results of parsing the options."
 opts.version = "0.0.1"

 opts.on("-s", "Enable short flag") {sflag = true}
 opts.on("--long", "Enable long flag") {longflag = true}
 opts.on("-b", "--both", "Enable both -s and --long"
         ) {sflag = true; longflag = true}
 opts.on("-c", "--count", "Add 1 to count") {count += 1}

 # Argument must match a regular expression.
 opts.on("-p", "--percent PERCENT", /[0-9]+%?/i,
         "Percent [50%]") {|arg| percent = arg.to_i}

 # Argument must match a list of symbols.
 opts.on("-f", "--fruit FRUIT",
         [:apple, :banana, :orange, :pear],
         "Fruit (apple, banana, orange, pear)"
         ) {|arg| fruit = arg}

 begin
   # Parse and remove options from ARGV.
   opts.parse!
 rescue OptionParser::ParseError => error
   # Without this rescue, Ruby would print the stack trace
   # of the error. Instead, we want to show the error message,
   # suggest -h or --help, and exit 1.

   $stderr.puts error
   $stderr.puts "(-h or --help will show valid options)"
   exit 1
 end

end

print <<EOF Short flag: #{sflag} Long flag: #{longflag} Count: #{count} Percent: #{percent}% Fruit: #{fruit} Arguments: #{ARGV.inspect} EOF</lang>

$ ruby takeopts.rb -h
Usage: takeopts [options] [arguments...]
This demo prints the results of parsing the options.
    -s                               Enable short flag
        --long                       Enable long flag
    -b, --both                       Enable both -s and --long
    -c, --count                      Add 1 to count
    -p, --percent PERCENT            Percent [50%]
    -f, --fruit FRUIT                Fruit (apple, banana, orange, pear)
$ ruby takeopts.rb -v 
takeopts 0.0.1
$ ruby takeopts.rb -b -c
Short flag: true
Long flag: true
Count: 1
Percent: 50%
Fruit: 
Arguments: []
$ ruby takeopts.rb -ccccp90% -f oran -- -arg
Short flag: false
Long flag: false
Count: 4
Percent: 90%
Fruit: orange
Arguments: ["-arg"]